MINNEAPOLIS (WCCO) – Four family members have now been convicted for participating in a sex trafficking ring that last about two years, extended to multiple Minnesota communities and victimized many vulnerable women.

On Wednesday, the Ramsey County Attorney’s Office announced that 30-year-old Otis Deno Washington, of St. Paul, was found guilty in Ramsey County District Court on multiple sex trafficking counts. According to a press release, they are: two counts of promotion of prostitution; two counts of solicitation, one involving a minor; and one count of conspiracy to commit sex trafficking.

He is slated to be sentenced on Jan. 9, 2014.

Washington was the last of his family members to be convicted. His brother and two of his uncles were charged and convicted in connection to the sex trafficking ring, which Ramsey County Attorney John Choi said “enslaved numerous women and girls.”

On Nov. 9, a jury found Washington’s brother, 27-year-old Antonio Washington-Davis, guilty on multiple counts. The brothers’ uncles – Robert James Washington and Calvin Roy Washington – both pleaded guilty to sex trafficking in July.

A criminal complaint says the sex trafficking ring spanned from September 2010 to July 2012, and that the brothers took drastic measures to keep their victims in line.

In April 2011, Antonio Washington-Davis brought one 15-year-old victim to a hotel in Ely, Minn., telling her it was “somewhere where you can’t talk to any of your family and won’t know where you are.”

The ring targeted mentally slow teenage girls, investigators said. One of the victims was bipolar, and another had a cognitive disorder. Others were runaways and living in homeless shelters.

The girls were photographed for elicit ads that were then placed on adult websites such as Backpage.com, the complaint said. They were forced to have sex with five or six customers a night, and at times up to 20. The elicit meetings were often arranged in private homes across the Twin Cities and in local motels.

The brothers are said to have kept nearly all the money and at times forced the girls to “walk the streets” to attract customers.

Choi said it took about six months to bust the ring.

To elude detection, the brothers used at least eight different e-mail addresses, along with 30 different phone numbers and some 100 prepaid credit cards to pay for their advertising.